Mineral lubricating oil containing wax alkylated hydrocarbon and a copolymer of ethylene and vinyl acetate



United States Patent 3,324,034 MINERAL LUBRICATING 01L CQNTAINING WAXALKYLATED HYDROCARBON AND A COPQLY- MER 0F ETHYLENE AND VINYL ACETATERichard E. Merz, Berkeley Heights, and Edward P. Cashman, Bayonne, N.J.,assignors to Esso Research and Engineering Company, a corporation ofDelaware No Drawing. Filed Aug. 10, 1965, ser. No. 478,724 3 Claims.(fill. 252-56) The present invention relates to novel lubricating oilcompositions, and especially to novel aviation lubricating oilcompositions, containing dissolved therein pour depressing amounts of amixture or blend of a wax alkylated aromatic hydrocarbon and a copolymerof ethylene and vinyl acetate.

In the past, when lubricating oil manufacturers desired to produce andmarket a product which would remain in a fluid state at low temperaturessuch as those encountered by aircraft based in cold climates, it wasnecessary to astringently refine fluid distillates used in preparingsuch lubricating oil fractions. Much effort was expended in dewaxing themineral oil fraction in order to obtain a low cold test oil, that is, alubricating oil exhibiting an increase of fluidity at low temperatures.This increase can be attributed to removal of the long needle-shaped waxcrystals, normally present in the mineral oil which interlocked and,thereby, entrapped oil. In later developments oils containingappreciable amounts of wax were found to be somewhat satisfactory underlow temperature conditions where materials were added which tended toinhibit the formation of the long needle-shaped crystals and insure freeflow at low temperatures. As employed herein, the temperature at whichan oil loses its properties of free flow is referred to as its pourpoint.

It is an object of the instant invention, therefore, to add a novalblend of additives to either wax free lubricating oils or to lubricatingoils containing wax in such an amount as to lower their pour point' Itis a particular object of this invention to markedly lower the dilutepour point exhibited by aviation lubricating oils.

Heretofore, a wide variety of compounds has been found suitable as pourpoint depressants for lubricating oils. One type of pour depressant canbe made by chlorinating paraffin wax and condensing the chlorinatedparaffin wax with an aromatic hydrocarbon such as benzene, naphthalene,or anthracene in the presence of a Friedel- Crafts type catalyst such asaluminum chloride. US. Patent Nos. 1,815,022, 2,087,682 and 2,174,246describe in detail procedures for making the chlorinated-waxaromatictype of pour point depressants and are incorporated herein by reference.Another type of pour point depressants for use in either lubricatingoils or in gasoline can be made by copolymerizing N-vnyl pyrrolidonesand their alkyl derivatives with alkyl esters of acrylic acid or ofmethacrylic acid. The preparation of these pour point depressants isdisclosed in detail in U.S. Patent 3,058,818 which is incorporatedherein by reference.

It was found, however, that these conventional pour point depressants,did not effectively lower the pour points of aviation oils to asufficient extent to permit such oils to be acceptable for enginesemployed in aircraft based in extremely cold climates. Similarly, it wasfound that a combination of wax alkylated aromatic pour pointdepressants with the heretofore mentioned ester type pour pointdepressants likewise failed to achieve a suflicient lowering of the pourpoint (particularly with reference to the dilute pour pointrequirements) to produce a blend of these two materials which wasconsistently acceptable for use in aviation oils. This failure resultedin the test for pour point properties of the oil, as well as in the testfor the dilute pour point properties of the oil; both tests presentlyemployed to determine the suitability of aviation oils.

In accordance with the present invention, it has been discovered that amineral lubricating oil composition comprising a major amount of ahydrocarbon mineral lubricating oil with a pour depressing amount of amixture of a wax alkylated aromatic hydrocarbon and a copolymer ofethylene and vinyl acetate find utility as an aviation lubricating oilwhich meets specifications both as to pour point and dilute pour point.This is indeed surprising for, as will be illustrated by comparativedata, neither of the materials of the mixture, when used alone,accomplishes the utility of the ethylene vinyl acetate copolymer, i.e.,each material shows practically no pour point depressant activities whenadded to lubricating oil. It is noteworthy that US. Patent 3,087,894teaches that the low molecular weight copolymers of ethylene and vinylacetate have no effect upon the pour point of lubricating oil andemphasizes the difference in structure between the wax associated withlube oils and the Wax associated with middle distillates. The copolymermolecular weights defined in such patent range from about 1,000 to about3,000. In the instant case, the molecular weights of ethylene-vinylacetate copolymers are higher but such higher molecular weights of theethylene-vinyl acetate copolymers have also heretofore been deemedessentially inactive as a pour point depressant. It was, therefore,surprising to discover that the use of a conventional pour pointdepressant, i.e., wax alkylated naphthalene, which by itself failed tomeet specifications as to dilute pour point, could be combined and yielda synergistically suitable aviation lubricating oil when combined withan ethylene-vinyl acetate copolymer which exhibited no effect per se asa pour point depressant in aviation lubricating oil.

The ethylene-vinyl acetate copolymers are obtained by heating a mixtureof ethylene and vinyl acetate at a temperature ranging between about andabout 400 C. with or without the presence of a solvent such as benzeneor heptane under super-atmospheric pressures of between about 100 andabout 2,000 atmospheres. Generally, the reaction is expedited if anoxidation catalyst such as a peroxide or hydroperoxide, for example,benzoyl peroxide or tertiary butyl hydroperoxide, is also present. Afterreaction the resulting copolymer is separated from the unreactedmonomers by flashing off the latter.

The mole ratio of ethylene to vinyl acetate may be varied to affect themelt index, inherent viscosity, as Well as the viscosity averagemolecular weight of the resultant copolymer. The melt index may rangefrom about 1 to about 1,000 but it is preferred to employ anethylene-vinyl acetate copolymer having a melt index ranging betweenabout 2 and about 500. These melt indices correspond to averagemolecular weights of between about 1500 and 500,000, preferably betweenabout 2000 and about 300,- 000, measured according to the method of K.Rast (Ber. 55, 1051, 3727 (1922)). For best results, an ethylene tovinyl acetate mole ratio in the copolymer of between about 0.25 :1 andabout 20:1 is used with the resultant copolymer having a melt index ofsomewhere between 2.5 and 475. A particularly preferred copolymer is onecontaining between 5 and 30 wt. percent of vinyl acetate and preparationdisclosed in US. Patent 3,058,818. To this base oil, referred to as (A),which had a pour point of F. and a dilute pour point of 40 F. whenmeasured in isooctane (Canadian military specification), was added, inseparate aliquots, (B) wax alkylated naphthalene, (C) a prior pourdepressant prepared according to specification of US. Patent 2,710,842,(D) a mixture of 75 wt. percent wax alkylated naphthalene and 25 wt.percent of a mixture of vinyl acetate with the ester prepared from Lorolalcohol and fumaric acid. Additionally, an aliquot was used containing ameasured amount of an ethylene-vinyl acetate copolymer, (E) containingabout 27% vinyl acetate and having a molecular weight by theaforementioned method of about 2,000. The following results wereobtained:

TABLE I Base Oil and Pour Depressant (A) (A) +(B) (A)+(C) i (AH-(D)(AH-( Concentration, Percent 0 0. 1.0 0. 5 1.0 0. 5 1.0 0. 5 1.0 PourPoint (ASTM D97-57) 0 l0 -15 -15 -l5 0 0 Dilute pour point (C anadlanMethod) --40 -45 40 -45 -40 -40 Could not be duplicated.

one preferably having a melt index ranging between 10 and 200. Thesecopolymers are oil soluble and may be preblended as a concentrate into alubricating oil fraction which serves as a vehicle. For convenience,this concentrate may contain from 40-75 Wt. percent of the blend of pourpoint depressants. The relative ratios of the depressants may vary overa considerable range but is generally between about 0.1 and 8 parts ofwax alkylated aromatic hydrocarbon per part of ethylene-vinyl acetatecopolymer. Highly effective results have been obtained where between 2and 3 parts of wax alkylated aromatic hydrocarbon are used per part ofethylene-vinyl acetate copolymer. The relative amount of additivesemployed in the lubricating oil composition ranges between about 0.01and about 5.0 wt. percent of the wax alkylated aromatic hydrocarbon andbetween about 0.02 and about 10 wt. percent of the vinylacetate-ethylene copolymer, both percentages being based on the totalweight of said lubricating oil composition. Specifically it is preferredto employ from about 0.05 up to about 0.5 wt. percent on the same basisof each of the two types of additives.

To be acceptable for commercial and military aircraft use, the aviationlubricating oils must meet the dilute pour point test which is denotedin the United States as US. Military Specification L6082C and in Canadaas Canadian Military Specification 3GP320. This test requires that thelubricating oil must have a dilute pour point of at least 50 F. for3GP320 and a dilute pour point of at least F. for L6082C under astandard set of conditions as outlined in those specifications. Effortshave been made to fulfill this requirement through the use ofcombinations of known lubricating oil pour point depressants, forexample, an aviation lubricating oil comprising 44.4 wt. percent of aMid-Continent lubricating oil stock having the specifications: +20 pourpoint, a viscosity index of 109.7, an API gravity of 305, a viscosity of59 SUS at 210 F. and 400 SUS at 100 F., and a flash point of 490 F.Cleveland open cup method (COC) admixed with 52.7% of a Mid-Continentlubricating oil fraction having the specifications: +15 F. pour point, aviscosity index of 100.5, an API gravity of 26.9", a viscosity of 146SUS at 210 F. and 22,224 SUS at 100 F., and a flash point of 580 F. COC.As in commercial operation, this was admixed with 2.9% of an N-vinylpyrrolidone type It is readily apparent from the above pour point anddilute pour point data that a combination of (A) with any of the otherfour materials tested as pour point depressants did not produce a dilutepour point which would meet specifications of -50 F. required by theCanadian military specification method. The base oil employed was acommercially available aviation lubricating oil.

The following examples are presented as illustrative of the inventionherein described but they are not intended to be limiting in any sense:

Example I An aviation lubricating oil base stock comprised the followingcomponents.

(a) 61 wt. percent Mid-Continent bright stock" of the followingcomponents.

Pour point F +20 Viscosity index 103 API gravity 26.50 Viscosity, SUS F1,192 Viscosity, SUS 210 F Flash point (COC) F 560 (b) 39 Wt. percentMid-Continent lubricating oil fraction (Barosa 56) of the followingspecifications:

Pour point F +20 Viscosity index 109.7 API gravity 30.5 Viscosity, SUS100 F 400 Viscosity, SUS 210 F 59 Flash point (COC) F 490 eordance withthe aforementioned US. military aviation F. and Run No. 20 ShOWlIlg adilute pour point of 5 5 specification. The data obtained are asfollows: F. The reference numbers which are not explained in the TABLEII Pour Point, Dilute Pour Point, F. in Run No. Percent by Wt. Additiveln Base Stock 9 7 Isooctane 1 LlEl'eptane-Xylol N +20 15 20 +20 35 35+15 35 35 +15 40 35 0. +15 35 40 /V B +15 40 35 0 1 E/VC-Elvax 460 +1535 35 0.1 E/VD +15 5 -15 0.3% wax alkylated naphthalene +15 35 35 0.1%E/VA.0.2% wax alkylated naphthalene +15 65 7 65 0.1% E/VA0.3% waxalkylated naphthalene +15 65 7 65 0.1% E/VB0.3% wax alkylatednaphthalene-" 05 7 65 0.1% E/VC0.3% wax alkylated naphthalene +10 55 600.1% E/VD0.3% wax alkylated naphthalene 35 0.3% E/VA0.3% wax alkylatednaphthalene +10 65 8 65 0.3% ENE-0.3% wax alkylated naphthalene +10 65 865 Specificati0n 9 -65 9 65 1 Canadian Military Specification Solvent. 2United States Military Specification Solvent. 3 Ethylene-vinyl acetatecopolymer, 27-29% 4 Ethylene-vinyl acetate copolymer, 27-29% 5Ethylene-vinyl acetate copolymer, 17-19% Ethylene-vinyl acetatecopolymer, 27-29% 7 65 or below. 8 65 or lower. P 65 max.

It should be noted that Run Nos. 1 through 9 did not achieve the dilutepour point specification of at least 50 F. At the same time Run Nos. 10through 13 and 15 and 16 did achieve the desired dilute pour pointspecifications.

Example II An additional series of runs were carried out using variousaviation base oil blends in which all base blends contained 2.9 wt.percent of an N-vinyl pyrrolidone .type pour depressant as disclosed inUS. Patent 3,058,818 and 0.32% of a bisphenol anti-oxidant. All runsalso contained 0.3 wt. percent of wax alkylated naphthalene. The dataobtained and an explanation of the base oils employed are as follows:

TABLE III Run No "I 17 18 I 19 20 Barosa 56 of Example I 52. 7 52. 7 325Neutral Oil 1 43. 7 Bright stock 2 44. 4 44. 4 Bright stock of Example I53.4 53. 4 N-vinyl pyrrolidone type polymer. 2. 9 2. 9 2. 9 2. 9Bisphenol anti-oxidant 0.32 0.32 0.32 0.32 Wax alkylated naphthalene-0.3 0. 3 0.3 0.3 E/V A 0. l 0. 1 Pour point, F -10 10 10 10 Dilute pourpoint, F. Heptane/ Xylene (2) 50 35 -55 Iso-octane (1) 40 50 35 -55Solvent dewaxed, solvent extracted, neutral Mid-Continent oil:

Pour point, F. +15 Viscosity index 100 API g'ravity 29.0 Viscosity, SUS325-340 Viscosity, SUS 50 Flash point (000 450 2 Mid-Continent brightstock Pour point, F +15 Viscosity index. 100. 5 API gravity 26.9Viscosity, SUS 100 F 2, 224 Viscosity, SUS 210 F 146 Flash point (COG),F 580 vinyl acetate, melt index -175 (ASTM D1238). vinyl acetate, meltindex 2.4-3.4.

vinyl acetate, melt index 125475.

vinyl acetate, melt index over 1000.

TABLE IV [Base oil same as for Run No. 18 on Table III] Run No 18 1 18 218 3 18 4 E/VA, percent 0.1 0.1 0.1 0.1 Pour 10 10 15 10 Dilute Pour inIsooctane 50 65 50 50 Dilute Pour in Heptane/Xylol 65 5 65 50 50 1Copolymer M.W. 3,500, Percent VA=18 (Allied Chemical, -400). 2 CopolymerMW ,000, Percent VA=6% (Allied Chemical, G-201). Copolymer M.W 6,500,Percent VA=27.

4 Copolymer M.W.=4,700, Percent VA=20.8.

6 65 or lower.

It is not intended that this invention be limited to the specificexamples presented by way of illustration. The scope of the invention islimited only by the appended claims.

What is claimed is:

1. An aviation lubricating oil composition having a dilute pour point of-50 F. or lower, as measured in isooctane, comprising a major amount ofa mineral hydrocarbon aviation oil; in the range of about 0.1 to about 5wt. percent of a wax alkylated aromatic hydrocarbon pour pointdepressant; and in the range of about 0.02 to about 10 wt. percent of acopolymer of ethylene and vinyl acetate pour point depressant, saidcopolymer having a melt index within the range of about 2 to about 500,an average molecular weight within the range of about 1500 and about500,000 and containing about 0.25 to about 20 moles of ethylene per moleof vinyl acetate; and wherein said wax alkylated hydrocarbon and saidcopolymer synergistically reduce said dilute pour point of said oil.

2. A composition according to claim 1, wherein said aromatic hydrocarbonis naphthalene, wherein the amount References Cited 3ft 23613533323253?2333 831 33522 ikifati UNITED STATES PATENTS .p n o a hydrocarbon isabout 2 to 3 times the amount of said 2960,4653 11/1960 Foehr F Xcopolymer 5 3,126,364 3/1964 Inycky] 25256 X 3. A composition accordingto claim 1, wherein said DANIEL E WYM AN P E oil contains about 0.3 wt.percent of wax alkylated naphrlmary xammer thalene and about 0.1 wt.percent of said copolymers. W. H. CANNON, Assistant Examiner.

1. AN AVIATION LUBRICATING OIL COMPOSITION HAVING A DILUTE POUR POINT OF-50*F. OR LOWER, AS MEASURED IN ISOOCTANE, COMPRISING A MAJOR AMOUNT OFA MINERAL HYDROCARBON AVIATION OIL; IN THE RANGE OF ABOUT 0.1 TO ABOUT 5WT. PERCENT OF A WAX ALKYLATED AROMATIC HYDROCARBON POUR POINTDEPRESSANT; AND IN THE RANGE OF ABOUT 0.02 TO ABOUT 10 WT. PERCENT OF ACOPOLYMER OF ETHYLENE AND VINYL ACETATE POUR POINT DEPRESSANT, SAIDCOPOLYMER HAVING A MELT INDEX WITHIN THE RANGE OF ABOUT 2 TO ABOUT 500,AN AVERAGE MOLDCULAR WEIGHT WITHIN THE RANGE OF ABOUT 1500 AND ABOUT500,000 AND CONTAINING ABOUT 0.25 TO ABOUT 20 MOLES OF ETHYLENE PER MOLEOF VINYL ACETATE; AND WHEREIN SAID WAX ALKYLATED HYDROCARBON AND SAIDCOPOLYMER SYNERGISTICALLY REDUCE SAID DILUTE POUR POINT OF SAID OIL.